\begin{tikzpicture}
    \tkzDefPoints{0/0/O}
    \tkzDefPoint(0:1.5){A}
    \tkzDefPoint(50:1.5){B}
    \tkzDefPoint(80:1.5){A'}
    \tkzDefPoint(130:1.5){B'}
    \tkzDefLine[altitude](A,O,B)  \tkzGetPoint{M}
    \tkzDefLine[altitude](A',O,B')  \tkzGetPoint{M'}

    \tkzDrawCircle[thick](O,A)
    \tkzDrawSegments     (O,A   O,B   A,B    O,M)
    \tkzDrawSegments[red](O,A'  O,B'  A',B'  O,M')
    \tkzMarkAngle[size=.6, -latex](A,O,A')
    \tkzDrawPoint(O)
    \tkzLabelPoints[below left](O)
    \tkzLabelPoints[right](A)
    \tkzLabelPoints[above right](B)
    \tkzLabelPoints[above](A')
    \tkzLabelPoints[above](B')
    \tkzLabelPoints[below, xshift=-.4em](M)
    \tkzLabelPoints[below, xshift=-.3em](M')
\end{tikzpicture}

